Due to the interconnection of keys on a keyboard, it is possible for a user key press of more than one key at a time to be erroneously detected to include a single unpressed key. It is possible for a single user key press (while other keys are depressed) to be perceived by the system as if the user had depressed more than one key simultaneously, i.e., the key pressed by the user and one or more additional keys. More specifically, a user key press of multiple keys at a time causes a signal path to be created in the keyboard such that a signal driven to detect a key press is received by an additional incorrect receiver indicative of a different key press than that pressed by the user. The receipt of a key press signal as a result of this type of occurrence is called a “key ghost.”
With respect to the key ghosting problem, prior solutions include forbidding users to press more than two keys of a keyboard at the same time.
Additionally, due to the construction and operation of the keys on the keyboard, a user key press may cause a key press to register as two key presses as the key moves back down due to an elastic reaction, e.g., movement of a mechanical spring against the key, and completes a contact on the keyboard for the duration of the user key press. That is, a key press results in detection of multiple key presses as a result of what is known as a “key bounce.” Different keyboards have different key bounce times due to the strength of the elastic mechanism for returning the key to its original position prior to a user key press.
With respect to the key bouncing problem, prior solutions include performing multiple keyboard key press detections in order to ensure stability of a received signal indicative of a key press; however, this approach slows down the detection system and the key press detection. Another prior solution included using electrical means, e.g., a capacitor, attached to each key on the keyboard in order to “debounce” the keys. However, this solution increases the cost of the keyboard in terms of component and manufacturing costs.